Negative effect of lanthanum tungstate on the mechanical properties of W-La2O3 alloys

Abstract

With the rapid development of the photovoltaic industry, tungsten alloys have been selected to replace the high‑carbon steel to fabricate the busbars for diamond wire saws due to their superior mechanical properties, and the La₂O₃ doped tungsten alloy has been widely used. However, the yield of eligible W alloy wires is not very high due to serious wire breakage problems during the production process, especially in the solid-liquid mixing route. To discover the possible reason, the commonly produced lanthanum tungstate (La₃₀W₁₇O₉₆) in the solid-liquid mixing route has been systematically studied in the work, and its possible influence on the mechanical properties is also explored. It is found that the La₃₀W₁₇O₉₆ leads to the formation of brittle second phases at grain boundaries (GBs), which weakens the intergranular bonding, resulting in a significant decrease in the compressive strength of tungsten alloys, manifested as intergranular fracture. Transmission electron microscopy (TEM) analysis reveals that these second phases are consisted of polycrystalline La₆W₂O₁₅, La₂W₃O₁₂ and amorphous states, and the La₃₀W₁₇O₉₆ can decompose into a more stable structure during sintering. This work highlights the destructive effect of La₃₀W₁₇O₉₆ on the intrinsic properties of tungsten alloys and provides a new perspective for solving the problem of tungsten wire breakage.